This disclosure relates to a gas turbine engine airfoil. More particularly, the disclosure relates to a cooling configuration in an airfoil squealer pocket.
Gas turbine engines typically include a compressor section, a combustor section and a turbine section. During operation, air is pressurized in the compressor section and is mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases are communicated through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and other gas turbine engine loads.
Both the compressor and turbine sections may include alternating series of rotating blades and stationary vanes that extend into the core flow path of the gas turbine engine. For example, in the turbine section, turbine blades rotate and extract energy from the hot combustion gases that are communicated along the core flow path of the gas turbine engine.
Many blades include internal cooling passages in their airfoils that supply a cooling fluid to cooling holes that extend through to the exterior surface of the airfoil. The airfoils extend from a platform to a tip. Some airfoil tip designs include a squealer pocket, which is a depression in the tip. Squealer pockets may include cooling holes, which deliver cooling fluid to the tip.
Turbine airfoils or outer air seals operate in an environment where the gas temperatures often exceed the material capability therefore they require cooling features to protect against damage. Cooling air from the compressor is used to provide internal convection cooling inside the airfoils. The problem with high amounts of cooling air is that less gas is available for work extraction, therefore, the engine efficiency is reduced with higher amounts of cooling. As demands for increase for higher thrust or efficiency, the airfoil designer is faced with increasing turbine inlet temperatures or reduced cooling flow allocation.
Blade tips are highly susceptible to erosion, oxidation, and thermal mechanical fatigue damage due to high thermal heat load. Consequently airfoil design and durability engineers currently implement cooling schemes that include squealer pockets, cooling holes, and/or tip shelves of any size to preserve the integrity of the tip. In many current designs, squealer pockets of various sizes and shapes are applied at the tip in conjunction with radial purge cooling holes. In some instances they may be used concurrently with tip shelves. While the squealer pocket itself reduces the external heat load on the tip due to causing flow separation within it and reducing thermal mass, the cooling hole supplies cooling air that mixes with the tip leakage flow and forms a pocket of cool air. The holes are generally angled at 90 degrees to the tip leakage, and provide film coverage downstream of the squealer pocket.